The Peltier effect, that helps in cooling, requires water in order to work. This is why the BLAUX Portable AC comes with a 300ml water tank, which is an adequate capacity to keep the cooling process going on for a long time. In case the water level goes low, the tank is easily refillable. Probably the most unique feature of the BLAUX Portable AC. It is a 200mAh lithium unit that can be charged via USB-C at DC5V, just like a smartphone. It is enough to keep the AC running at a maximum of 8 hours. Lastly, the BLAUX Portable AC has an air filter inside of it, which is similar in looks and size as the one found in cars. It helps filter out dust particles and ionizes the air in order to neutralize contaminants that might cause allergies. The BLAUX Portable AC is definitely worth the money .